Material treatment apparatus

ABSTRACT

Material treatment apparatus comprises a chamber, a plurality of first electrodes having opposed end surfaces adjacent one another to define a passage having an axis passing between the end surfaces. A second electrode structure has its end surface spaced from the first electrodes and aligned with the passage axis. Circuit means energizes the first and second electrodes to produce a high intensity electric arc condition to establish an elongated high enthalpy zone coaxial with said passage axis. Entrance port means in the chamber introduces material to be treated into the zone between the first and seconds electrode structures for flow through the passage defined by the faces of the first electrodes and the high enthalpy zone.

May 9, 1972 L. w. SCAMMON, JR

MATERIAL TREATMENT APPARATUS 3 Sheets-Sheet 1 6 5 4 @4 4 O OJ 6 4 4 l v Q N l w n G F H 60 92 FIG? TEMP "F WCHES FROM 6 TANK CENTER May 9, 1972 L. W. SCAMMON, JR

MATERIAL TREATMENT APPARATUS 3 Sheets-Sheet 2 Filed Nov. 14, 1969 FIG 3 May 9, 197 w. scAMMoN, JR

MATERIAL TREATMENT APPARATUS Filed Nov. 14, 1969 3 Sheets-Sheet 3 United States Patent 3,661,764 MATERIAL TREATMENT APPARATUS Lawrence W. Scammon, Jr., Concord, N.H., assignor to Humphreys Corporation, Bow, N .H. Filed Nov. 14, 1969, Ser. No. 876,741

' Int. Cl. C22d 7/08 US. Cl. 204-325 35 Claims ABSTRACT OF THE DISCLOSURE Material treatment apparatus comprises a chamber, a plurality of first electrodes having opposed end surfaces 'adjacent'one another to define a passage having an axis SUMMARY OF THE INVENTION This invention relates to high temperature technology apparatus and more particularly to apparatus which provides a high enthalpy thermal environment for the treatment of material and/ or the production of radiant energy.

It is frequently desired to subject material to a high enthalpy thermal environment to produce a pyrometallurgical or a chemical reaction, for example. A variety of apparatuses have been. proposed for these purposes. In general, commercially feasible apparatus for producing chemical reactions in high temperature thermal environments with particulate material such as ores, concentrates and residues containing metal values have been of the batch vtype. Difficulties have been experienced in endeavoring to introduce solid or liquid phase reactants into thehigh enthalpy thermal environment produced by an electric arc in sufiicient quantities to be useful without extinguishing the are or plugging the gap between the electrodes. -Also, the residence time of the reactants in the arc zone of most prior art apparatus was too short to .achieve'useful results. Sheer and Korman, to overcome these problems, proposed apparatus employing graphite electrodes in which the ore to be processed was a component part of the electrodes and was gradually introduced into the arc zone as the electrodes were consumed. Due inpartto the cost of fabricating electrodes used in such apparatus, such apparatus has not received significantcommercial acceptance. Bainbridge (US. patent application Ser. No. 826,991, filed May 22, 1969) describes apparatus in which an elongated high enthalpy thermal zone is provided by a high intensity are between carbon electrodes in an arrangement in which particulate materialzis .fed smoothly into and through the arc zone with resulting significantpyrometallurgical processing of the feed material. -It is an object of this invention to provide novel and improvedsapparatus that produces a high temperature environment and may :be advantageously employed for;.treating gases, liquids. and solid material.

Another object-of the invention is to provide novel and improved apparatus; for subjecting material to the action of a high intensity electric are for heataffecting the material and/or producing a chemical reaction in a manner thatprovides a stable aroand high enthalpy thermal zone and in which material may. be efiiciently introduced into the arc zone. V I 7 ice Another object of the invention is to provide novel and improved apparatus of the continuous process type for subjecting material to a high enthalpy thermal environment.

Material treatment apparatus constructed in accordance with the invention includes a chamber in which a plurality of spaced first electrodes are disposed so that their respective end surfaces are adjacent one another and define a passage having an axis that passes between the end surfaces of the electrodes. A second electrode is spaced from the first electrodes and aligned with the passage axis. The apparatus further includes circuit means for'energizing the first and second electrodes to produce an arc and a resulting elongated high enthalpy zone that is coaxial with the passage axis, the high enthalpy zone extending away from the sides of the first electrodes remote from the second electrode. Entrance port means are provided for introducing matter to be treated into the arc between the first and second electrodes and fiow along the passage axis through the passage defined by the faces of said first electrodes and said high enthalpy zone. This invention provides apparatus especially adapted to process particulate material on a continuous basis. The electrode geometry produces a stable arc configuration and a stable elongated high enthalpy zone.

In particular embodiments of the invention, the first electrodes are anodes symmetrically arranged about the axis of the passage and, where graphite is employed as the anode material, the apparatus preferably includes drive means for concurrently rotating and advancing the anode electrodes to maintain the electrode end surfaces so that they define a passage of relatively uniform dimension. Other anode configurations such as the porous anode in which gas is flowed through the anode face are also useful in the practice of the invention. In such embodiments the second electrode is a cathode, which may be of various configurations. For example, in one embodiment a single metal cathode having a gas shielded tapered tip is employed and in another the cathode is a consumable carbon rod. Other cathode structure arrangements may include an annular (hollow) electrode or a group of electrode elements. The center of the end surface (or surfaces) of the cathode structure is located on the axis of the passage between the end surfaces of the anode electrodes. The adjacent end surfaces of graphite anodes, when energized in high intensity are mode in accordance with the invention, are incandescent and the carbon is sublimating so that a concentrated passage zone, the walls of which are intensely hot, is provided.

The established arc of the invention is characterized by a spacially stable cathode jet which extends through the passage defined by the end surfaces of the anodes along the axis thereof and does not touch the anode electrodes themselves. Circulation of gases appears to include flow of gases upward between the spaced anode electrodes and downwardly through the passage between the anode end surfaces and the cathode jet, particularly where no auxiliary gas flow is imposed as for example an auxiliary gas used as a carrier gas for particulate material. Extending below the anodes as an extension of the cathode jet, is a tail flame that may be up to five feet or more in length.

' Plural material injection passages that are symmetrically arranged with respect to the axis of the apparatus are preferably employed when, for example, particulate material is to be treated. The passages direct the material to be treated into the arc between the first and second electrodes and flow through the passage between the end faces of the first electrodes and then along the apparatus axis through the elongated high enthalpy zone. It is. preferred that the injection pasages terminate near (within about one half inch) of the plane of the tip of the secondelec,

trode or extend beyond that plane toward the first electrodes to avoid contamination of the second electrode. The gaseous, liquid or solid material to be treated is introduced through these passages with a positive velocity (a carrier gas velocity greater than ten feet per second is employed in the disclosed embodiments) and enters smoothly into the cathode jet zone between the first and second electrodes for initial thermal exposure, then flows into the passage defined by the intensely hot electrode faces of the first electrodes for further thermal exposure, and subsequent continuing thermal exposure as it flows through the elongated tail flame portion of the are system. The gas velocities in the arc zone in this apparatus provide a residence time for particles passing through the high enthalpy zone up to in the order of 500 milliseconds.

In a common cathode plural anode DC furnace arrangement, the axes of the injection passages preferably form an angle of less than 45 to the passage axis and intersect the passage axis above the plane of the first electrodes. An injection angle of 37 /2 has been found to produce a particularly advantageous result. Further, it is preferred that particulate material be entrained in a carrier gas which may be a component of or contribute to a chemical reaction and which imparts positive velocity to that introduced material. Carrier gas velocities of 50-90 feet per second produce satisfactory results and lesser or greater carrier gas velocities are also appropriate for particular materials and applications of the invention. A variety of gases may be employed including air oxygen, carbon monoxide, methane, nitrogen, chlorine, argon and hydrogen. Hydrogen is advantageously employed in some processes as anode consumption rates are reduced by up to two-thirds when using hydrogen instead of air. The are operates at a higher voltage with hydrogen and is smaller in diameter and the cathode jet is further from the incandescent ends of the graphite anodes.

This apparatus provides a stable elongated high enthalpy zone for the treatment of material. The apparatus is particularly adapted to treat particulate material, both for effecting chemical reactions, as for example in pyrometallurgy, and for modifying the physical configuration of the particles (for example, spherodizing). The invention may also be used for other purposes for example as a light source, as a heat source in which the tail fiame impinges on the surface of external material for such purposes as to control a cooling rate, or flame spraying.

Other objects, features and advantages of the invention will be seen as the following description of particular embodiments of the invention progresses, in conjunction with the drawings, in which:

FIG. 1 is a diagrammatic elevational view, in partial section, of apparatus constructed in accordance with the invention;

FIG. 2 is a top view of the arc head assembly furnace shown in FIG. 1 with the cathode and material feed assembly removed;

FIG. 3 is a sectional view showing details of the cathode-material feed assembly;

FIG. 4 is a sectional view showing details of an anode assembly;

FIG. 5 is a sectional view taken along the lines 5-5 of FIG. 4;

FIG. 6 is a graph indicating operating conditions inthe furnace;

FIGS. 7 and 8 are diagrammatic views indicating ferent modes of operation of the furnace; and 6 FIG. 9 is a diagrammatic view of a modified embodiment of the furnace shown in FIG. 1.

With reference to FIG. 1, the apparatus includes a main chamber 10 having an inner wall constructed of a corrosion resistant material such as stainless steel and a spaced outer wall of mild steel. The chamber includes a domed upper wall 12 having a central opening therein in which an arc head assembly 14 is mounted; cylindrical difmain section 16 is five feet in diameter and forty inches long that has a clean out port closed by door 18 2 /2 feet in diameter which carries a water cooled window 20, and optionally one or more additional ports; and a lower section 22 five feet in length that tapers to an exit port eight inches in diameter and is secured by flange 24 to the cylindrical section 16. Conventional processing equipment such as a scrubber 26 may be secured to the lower end of tapered section 22 by means of flanges 28. Cooling water is circulated throughthe upper sections 12 and 16 of the chamber assembly 10 by means of connections 30 and through the lower section 22 of the assembly 10 by means of connections32. Bafiles between the stainless steel inner walls and the mild steel outer walls direct the circulation of cooling water.

The are head assembly includes a cylindrical housing 40 of sixteen inches inner diameter which has a lower flange 42 mounted on a mating surface of domed section 12 of tank 10 and an upper flange 44 on which is secured a glass epoxy insulator disc 45 and plate 46 which carries a cathode electrode and material feed assembly 50. Extending radially outward from housing 40 are three anode assemblies, each of which includes a carbon electrode 52, an electrode drive assembly 54, an electrical connection assembly 56 and water cooling connections 58. A top view of the furnace structure with the cathode and material feed assembly removed is shown in FIG. 2.

The tops of the anodes 52 are located in a plane one inch below the tip of the cathode and the end of each anode is spaced about one inch from theaxis of the furnace thus defining a passage approximately two inches in diameter.

Details of the cathode-material feed assembly are shown in FIG. 3. That assembly includes a nozzle plate 60 mounted on plate 46 and sealed by O-ring 62. Three material feed passages 64, each 4 inch in'diameter and disposed at an angle of 37 /2 to the vertical, pass through plate 60, have exit ports /a inch from the furnace axis, and are connected to feed tube 66 via nipple 68 which is sealed by O-ring 70. Feed passages '64 employed in modifications of this embodiment included inch diameter passages. In the spherodizing of particulate material it has been found advantageous to utilize an exit port of larger dimension than' the feed passage, for example, a feed passage diameter of inch and an exit port diameter of inch. The angle of injection ports 64 should be such that an extension of the port axis intersects the axis of the cathode above the plane" of top surfaces of the anodes. While this angle is somewhat: dependent on the nature of the particulate material being processed, a larger angle (e.g. 45) frequently causes the powder to pass entirely through the cathode jet while a smaller angle (30") does not introduce all of the powder into the cathode jet prior to passage through the enclosed zone defined by the faces of the anodes. A nozzle insert 72' provides a taper from the main bore of plate 60 (1% "inch in diameter) to an exit diameter of /2 inch at nozzle exit 74. Cooling chamber 76 in insert 72 is supplied with coolant through passage 78.

Seated in plate 60 is a manifold structure formed by ring 80 and sleeve 82. An annular channel .84 in ring 80 provides a distributing chamber which has a series of" ports 86 in its inner wall that provide passages for. introduction of a suitable shielding gas, such as argon, through a i tappe'd fitting (not shpwn) into the nozzle structure.Mo'unted inside of sleeve 82 is a nylon insulating cylinder 90 which supports a cylindrical cathode electrode assembly 9 2'that is 1 inch in diameter. The cathode electrode assembly 92 includes an upper cylindrical section 94 of copper, an intermediate cylindrical section 96 of copper and a conical tungsten tip 98 that tapers to a flat tip 100 4; inch in diameter. A conical tip angle of, 60.is preferredforthe cathode although satisfactory results have beenobtained with cathode tip angles in the range of.40-. Tube 102, supported coaxially within the cathode assembly 92, ap-

pliescooling water for passage down through tube 102 and return upwardly through the surrounding annulus defined between tube 102-and the cathode assembly 92.

Details of an anode assembly are shown in FIGS. 4 and 5. The graphite anode electrode 52 is supported by two rollers 122, 124 in the anode drive assembly 54 and a tellurium copper bushing insert 120 in the electrical connector assembly 56. Insert 124 is carried by tellurium copper disc 126 (1.230 inch in thickness and eleven inches in diameter) which with glass epoxy insulator discs 128 is clamped between flange 130 of the water cooled arc head assembly housing 40 and flange 132 of water cooled spacer cylinder 134. Disc 126 has two passages through it which are connected by a passage in block 136 so to provide a flow path for cooling water through the copper disc. The anode electrode 52 is biased into engagement with bushing'120 by graphite probe 140 that has follower 142 secured to it and which in turn is biased by an assembly that includes spring 144, block 146, and clamping plate 148 which is secured to the insulator discs 128 by bolts 150. By appropriate selection of the size of rollers 122, 124 and bushing 120, carbon anode rods of one inch diameter, 1% inch diameter or 1 /2 inch diameter may be employed in this apparatus.

" The anode drive assembly 54 is clamped between flange 160 of spacer cylinder 134 and flange 1-62 of seal support cylinder 164. Glass epoxy insulator discs 166 are positioned on either side of the drive assembly which includes a base structure 170 which supports three shafts 172, 174 and 176. Tie rods 180' secure the components of the shaft support assembly-together. A worm gear 182 is mounted on shaft 172 and engaged by Worm 184 which is driven via shaft 186 and gear reducer 188 by drive motor 190 mounted on bracket 192. At the opposite end of shaft 172 from gear 182 is mounted a sprocket 194. Similar sprockets 196, 198 are mounted in corresponding locations on shafts 174 and 176. A chain 200 is trained around these three sprockets and is maintained in tension by a biasing idler sprocket 202 and spring 204. Mounted on shafts 174 and 176"-are support rollers 122 and 124, respectively. A toothed "roller 206 is mounted on shaft 172. The axis of roller 206 is skewed at an angle of 1 /2 so that as shaft 172 is driven by motor 190, anode rod 52 is slowly advanced While being continuously rotated. A gas seal structure-152 is preferably disposed outwardly of the drive assembly. As shown in'FIG. 2, structure 152 includes two annular, flexible wipers 154 which define an annular chamber 15'6into which a sealing gas is introduced through passage-158. Nitrogen-at a pressure of p.s.i.g. is suitable for many applications.

In'typical operation in an air environment, a main DC power supply 208 applies an open circuit voltage of one 'hun dred sixty volts between the cathode 92 and an'odes52.' An auxiliary, 300 volt open circuit, starting power supply is connected between cathode 92 and sleeve 82, and an arc is initiated with a Welding type arc starter in -theconica'l space between cathode tip 100 and the surrounding nozzle insert 72. Argon shielding gas, introducedthrough chamber 84 and ports '88, blows the arc downwardly from the tip 100 of the cathode 92 to strike the -anodes S2; The auxiliary power supply is then dis- ..connected and the current supplied by the main power supply 208 is,increa sed to established an arc environment includinga cathode jet 210 and a tail flame 212 that extends fromthe anodes 52 down into the tapered section 22 of the tank 10. In an air environment a typical arc voltagei s one hundred volts and in a hydro- 20,000 P. FIG;"6 is a graph indicating gas temperatures in 'thetail flame 212 inthe furnace when operating at powers" of 210 kilowatts and 300 kilowatts. These temperatures were measured thirty inches below the graphl t m ite anodes 52 with an unshielded thermocouple. As indicated in FIG. 6, with a power of 210 kilowatts the gas temperature is about 750 adjacent the walls of the tank 10 and increases to a temperature of at least 2500 F. in the center of the tail flame 212. At a power of 300 kilowatts, the temperature adjacent the tank wall is about 900 F. and increases to at least 3,000 F. at the center of the tail flame.

In a typical operation, the tank 10 is initially cleaned of all previous run material and each powder feeder (one coupled to each passage 64) is charged with an equal amount of particulate feed material. The electrode system is energized and allowed to operate until there is a negligible amount of oxygen in the tank. Carrier gas flows are adjusted to the desired values and the powder feeders are turned on at preset feed rates. The cathode jet 210 entrains the particles and sweeps them down through the passage defined by the incandescent sublimating end surfaces of the anodes 52 and along the high enthalpy zone of the tail flame 212. A run is terminated when any one powder feeder becomes empty. A variety of particulate materials have been processed with this apparatus. The following table is an indication of types of materials and the operating conditions of the apparatus.

Input Arc particle Feed power mesh rate, kilo- Material size lbs./hr. Carrier gas, s.c.f.h. watts Steel shot 30 380 Nitrogen, 155; 2%

hydrogen, 98.

Tulameen sand. l50 30 210 lrco -200 45 Carbon monoxide, 345. 218

Rutile and carbon -30 45 0 253 Ilme -30 60 Hydrogen, 900 270 Zircon 30 97 Air, 345 231 --30 84 Methane, 458 277 30 60 Carbon monoxide, 345 258 30 77 Hydrogen, 900 276 320 Air, 280 270 In all these runs, the particles had been melted and rehardened and essentially were all spherical. The power required per pound of feed material is significantly lower than prior plasma systems.

Anode consumption is reduced by up to two thirds when hydrogen is used as a carrier gas instead of other gases such as air, argon, nitrogen or chlorine. A comparison of the shape of the cathode jet when employing air and hydrogen is shown in FIGS. 7 and 8. The are operates at a higher voltage with hydrogen, thus reducing current for a given power level. Further the hydrogen cathode jet appears to be smaller in diameter than the cathode jet in air, and thus is further away from the incandescent ends of the graphite anodes. The graphite anode consumption rate at an operating power of 300 kilowatts is approximately twelve pounds per hour with either air or nitrogen as a carrier gas and approximately four pounds per hour with hydrogen.

A second embodiment shown in FIG. 9 employs three, one and one half inch diameter graphite anodes having similar drive units assemblies 54' and electric power connector assemblies 56'. The cathode 92' is one inch diameter graphite rod, and a drive assembly 220 and electrical conductor assembly 222 similar to those employed in the anode electrodes is utilized. This embodiment was operated with an arc voltage of volts, an anode'cu'rrent of 700 amperes and a cathode current of 2100 amperes.

In still another embodiment, a gas shielded 'rnetal cathode and three 1% inch O.D. non-rotating graphite anodes were employed, the cathode being spaced one inch from the plane of the anodes. In a test of this embodiment with a 1.9 inch O.D. pipe calorimeter extending transversely through the tail flame at a point about seven inches below the anodes, ho substantial change in the heat to the calorimeter was detected over a range of supplemental gas fiows from no flow to a flow rate of 200 s.c.f.h.

Thus it will be seen that this invention provides apparatus particularly adapted for subjecting particulate material to significant heat treatment and/or chemical processing and has particular value in the pyrometallurgical fields. While particular embodiments have been shown and described, various modifications thereof will be apparent to those skilled in the art and therefore it is not intended that the invention be limited to the disclosed embodiments or to details thereof and,departures may be made therefrom within the spirit and scope of the invention as defined in the claims.

What is claimed is:

1. Material treatment apparatus comprising a chamber, a plurality of individual elongated first electrodes, the end surfaces of said first electrodes being disposed in adjacent opposition to one another to define a passage having an axis passing between said end surfaces and the axes of said first electrodes extending radially outward from said passage, a second electrode structure having its end surface spaced from said first electrodes and aligned with said passage axis, circuit means for energizing said first and second electrodes to produce a high intensity electric arc condition between said second electrode and said first electrodes to establish an elongated high enthalpy zone coaxial with said passage axis, and entrance port means in said chamber for introducing material to be treated into the zone between the end surface of said second electrode and before the passage defined by said end surfaces of said first electrodes for fiow through the passage defined by the faces of said first electrodes and said high enthalpy zone.

2. The apparatus as claimed in claim 1 wherein said first electrodes are connected to said circuit means as anodes and said second electrode is connected to said circuit means as a cathode.

3. The apparatus as claimed in claim 2 wherein said anode electrodes are made of carbon containing material.

4. The apparatus as claimed in claim 3 wherein said circuit means is adapted to energize said anode electrodes so that said end surfaces are sublimating.

5. The apparatus as claimed in claim 2 wherein said end surface of said cathode electrode includes a tapered tip and further including means for supplying a shielding gas for flow across said tapered tip.

6. The apparatus as claimed in claim 5 wherein the angle of said cathode tip is in the range of 40-120".

7. The apparatus as claimed in claim 2 wherein said cathode is made of a carbon containing material.

8. The apparatus as claimed in claim 2 wherein said circuit means energizes said cathode to establish a spacially stable cathode jet which extends through the passage defined by the end surfaces of said anodes.

9. The apparatus as claimed in claim 1 wherein said entrance port means has an injection axis which intersects said passage axis above the plane defined by the tops of end surfaces of said first electrodes.

10. The apparatus as claimed in claim 1 wherein said entrance port means is disposed so that material is discharged therefrom at an injection angle of less than 45 to said passage axis.

11. The apparatus as claimed in claim '1 wherein said entrance port means includes a plurality of injection passages symmetrically disposed about said passage axis.

12. The apparatus as claimed in claim 1 wherein said entrance port means terminates in a region between a plane defined by said end surfaces of said first electrodes and a parallel plane disposed from the end surface of said second electrode structure at a distance of less than one half the distance between the end surfaces of said first and second electrode structures.

13. The apparatus as claimed in claim 1 and further including means for introducing material into said zone with a positive velocity.

14. The apparatus as claimed in claim 1 and further including feed passage means for supplying material to said entrance port means and wherein the cross-sectional dimension of said entrance port means is greater than the cross-sectional dimension of said feed passage means.

15. The apparatus as claimed in claim 1 and further including means for entraining particulate material to be processed in a carrier gas that has a velocity greater than ten feet per second.

16. The apparatus as claimed in claim 15 wherein Said entrance port means has an injection axis which intersects said passage axis above the plane defined by the tops of end surfaces of said first electrodes.

17. The apparatus as claimed in claim 16 wherein said entrance port means includes a plurality of injection passages symmetrically disposed about said passage axis.

18. The apparatus as claimed in claim 17 wherein said injection passages terminate in a region between a plane defined by said end surfaces of said first electrodes and a parallel plane disposed from the end surface of said second electrode structure at a distance of less than one half the distance between the end surfaces of said first and second electrode structures. h

19. The apparatus as claimed in claim 18 wherein said injection passages are disposed so that material is discharged therefrom at an injection angle of less than 45 to said passage axis.

20. The apparatus as claimed in claim 19 and further including feed passage means for supplying material to said entrance port means and wherein the cross-sectional dimension of said entrance port means is greater than the cross-sectional dimension of said feed passage means.

21. The apparatus as claimed in claim 1 further including means for rotating and advancing said elongated first electrodes as material is being fed through said passage to compensate for changes in the dimensions of said passage.

22. The apparatus as claimed in claim 21 wherein said first electrodes are made of carbon containing material and are connected to said circuit means as anodes, said second electrode is connected to said circuit means as a cathode, and said circuit means energizes said anodes so that said end surfaces are sublimating.

23. The apparatus as claimed in claim 22 wherein said end surface of said cathode includes a conical tip, the angle of which is in the range of 40420", and further including means for supplying a shielding gas for flow across said conical tip.

24. The apparatus as claimed in claim 23 wherein said circuit means is adapted to energize said cathode to establish a spacially stable cathode jet which extends through the passage defined by the end surfaces of said anodes. H p

25. The apparatus as claimed in claim 24 wherein said entrance port means has an injection axis which intersects said passage axis above the plane defined by the tops of end surfaces of said first electrodes.

26. The apparatus as claimed in claim 25 wherein 'said entrance port means includes a plurality of injection passages symmetrically disposed about said passage axis and said entrance port means terminates in a region between a plane defined by said end surfaces of said first electrodes and a parallel plane disposed from the end surface of said second electrode structure at a distance of less than one half the distance betwten the end surfaces of said first and second electrode structures.

27. The apparatus as claimed in claim 25 and further including means for entraining particulate material to be processed in a carrier gas that has a velocity greater. than ten feet per second. 1 i i 28. The apparatus as claimed in claim 27 and further including feed passage means for supplying material to said entrance port means and wherein thecross-sectional dimension of said entrance port means is greater than the cross-sectional dimension of said feed passage means.

29. Apparatus for producing a high enthalpy zone comprising a plurality of elongated anode electrodes, means supporting said anode electrodes symmetrically about an axis with their end surfaces adjacent one another to define a passage coaxial with said axis, a cathode electrode structure, means supporting said cathode structure spaced from said anode electrodes with the center of its end surface portions aligned With said passage axis, and circuit means for energizing said anode and cathode electrodes to establish a spacially stable cathode jet which extends along said axis through the passage defined by the end surfaces of said anode electrodes without touching said anode electrodes and an effiuent tail fiame coaxial with said passage axis, said tail flame extending away from said anode electrodes on the side remote from said cathode electrode structure as an extension of said spacially stable cathode jet.

30. The apparatus as claimed in claim 29 further inc'iuding means for rotating and advancing said elongated electrodes to maintain the dimensions of said passage substantially constant.

31. The apparatus as claimed in claim 29 wherein said anode support means includes at least two spaced support elements and further including means for feeding said elongated anode electrodes toward said axis to maintain the dimensions of said passage substantially constant.

32. The apparatus as claimed in claim 31 and further including gas seal structure mounted outward of said feeding means, said gas seal structure including two spaced wiper members that define walls of an annular zone about a portion of the length of each elongated electrode and means for supplying gas to said annular zone.

33. The apparatus as claimed in claim 29 wherein said circuit means is adapted to energize said anode electrodes so that said end surfaces are sublimating.

34. The apparatus as claimed in claim 29 wherein said end surface of said cathode electrode includes a tapered tip and further including means for supplyin a shielding gas for flow across said tapered tip.

35. The apparatus as claimed in claim 34 wherein the angle of said cathode tip is in the range of 40120.

References Cited UNITED STATES PATENTS 3,051,639 8/1962 Anderson 204-171 3,390,980 7/1968 Orbach et al. 204-323 3,332,870 7/1967 Orbach et al. 204-328 3,247,014 4/1966 Goldberger et al. 204-328 JOHN H. MACK, Primary Examiner N. A. KAPLAN, Assistant Examiner US. Cl. X.R. 204-323 

